Serotype-specific mortality from invasive Streptococcus pneumoniae disease revisited

Case-fatality ratio of bacterial meningitis in the African meningitis belt: we can do better

In the African meningitis belt, reported case-fatality ratio (CFR) for meningitis are usually calculated on the basis of presumed cases. We reviewed 3509 presumed cases of bacterial meningitis reported in Niger for which a cerebrospinal fluid (CSF) sample had been tested later at the reference laboratory. The main aetiologies were Neisseria meningitidis (1496 cases), Streptococcus pneumoniae (303 cases) and Haemophilus influenzae (105 cases). The CFR of meningococcal meningitis was lower for serogroup A (5.5%) than for serogroups X (12%) and W135 (12.7%). With a CFR of 49.8%, pneumococcal meningitis, albeit representing only 20.7% of confirmed cases, accounted for 50% of the deaths. The disease burden of pneumococcal meningitis must be better taken into consideration in the future. As most treatments are presumptive, there is a urgent need for an easy-to-administer, cheap first-line treatment effective on N. meningitidis as well as on S. pneumoniae and H. influenzae that would replace the single-dose oily chloramphenicol treatment which is the most frequent treatment administered today, independent of microbial aetiology and season. The development of diagnostic tools really suitable for remote health facilities also is an urgent challenge.

Antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae isolated from patients with community-acquired pneumonia and molecular analysis of multidrug-resistant serotype 19F and 23F strains in Japan

A nationwide study was undertaken to determine the susceptibility to penicillin and serotypes of Streptococcus pneumoniae in Japan. S. pneumoniae was isolated from 114 adult patients with community-acquired pneumonia over 22 months at 20 hospitals and medical centres in different regions in Japan. All but five isolates were from sputum. Forty-eight isolates (42.1%) were susceptible, 40 (35.1%) showed intermediate resistance (MIC, 0.12-1.0 microg/ml) and 26 (22.8%) were resistant (MIC, >or=2.0 microg/ml) to penicillin G. All isolates were susceptible to ceftriaxone (breakpoint 1 microg/ml), imipenem (4 microg/ml) and vancomycin (4 microg/ml). Most were resistant to erythromycin, clarithromycin and azithromycin; only two were resistant to levofloxacin. Differences were found in the distribution of serotypes among isolates showing susceptibility to penicillin (predominant types 3, 6B, and 19F), intermediate resistance (6B, 14, 19F, and 23F) and full resistance (19F and 23F). PFGE typing showed that 14 of the 25 strains of serotype 19F had a single DNA profile, pattern A, a pattern closely similar to that of the Taiwan multidrug-resistant 19F clone. Twelve pattern A strains were not susceptible to penicillin but carried the macrolide resistance gene mef(A). The DNA profiles of the 15 strains of 23F were also heterogeneous but six were highly similar (pattern b) yet distinct from the Spanish multidrug-resistant 23F clone although possibly related to the Taiwan multidrug-resistant 23F clone. The pattern b strains were not susceptible to penicillin and also harboured either mef(A) or erm(B). Our results indicate that multidrug-resistant pneumococci are spreading rapidly in Japan. Efforts to prevent the spread of the pandemic multidrug-resistant serotypes should be intensified.

Differential activation of inflammatory pathways in A549 type II pneumocytes by Streptococcus pneumoniae strains with different adherence properties

Background

Adherence of Streptococcus pneumoniae bacteria to lung cells is a first step in the progression from asymptomatic carriage to pneumonia. Adherence abilities vary widely among S. pneumoniae patient isolates. In this study, the binding properties of S. pneumoniae isolates and the effects of binding on activation of the Nuclear Factor-Kappa-B (NFκB) pathway and cytokine secretion by type II pneumocytes were measured.

Methods

Mechanisms of high- and low-binding S. pneumoniae adherence to A549 cells were investigated by blocking putative receptors on bacteria and host cells with antibody and by eluting choline-binding proteins off of bacterial surfaces. NFκB activation was measured by western blot and immunocytochemistry and cytokine secretion was detected by a protein array.

Results

This study shows that S. pneumoniae isolates from pneumonia patients (n = 298) can vary by as much as 1000-fold in their ability to bind to human lung epithelial cells. This difference resulted in differential activation of the NFκB pathway. High-, but not low-binding S. pneumoniae used Choline-binding protein A (CbpA) to bind to complement component C3 on epithelial cell surfaces. Interleukin-8 (IL-8) was the only cytokine secreted by cells treated with either low- or high-binding S. pneumoniae.

Conclusion

These results indicate that S. pneumoniae clinical isolates are not homogeneous in their interaction with host epithelial cells. The differential activation of host cells by high- and low-binding S. pneumoniae strains could have implications for the treatment of pneumococcal pneumonia and for vaccine development.

Identification of invasive serotype 1 pneumococcal isolates that express nonhemolytic pneumolysin

Recently, there has been an increase in invasive pneumococcal disease (IPD) caused by serotype 1 Streptococcus pneumoniae throughout Europe. Serotype 1 IPD is associated with bacteremia and pneumonia in Europe and North America, especially in neonates, and is ranked among the top five most prevalent pneumococcal serotypes in at least 10 countries. The currently licensed pediatric pneumococcal vaccine does not afford protection to this serotype. Upon screening of 252 clinical isolates of S. pneumoniae, we discovered mutations in the pneumolysin gene of two out of the four serotype 1 strains present in the study group. Analysis of an additional 28 serotype 1 isolates from patients with IPD from various Scottish Health Boards, revealed that >50% had mutations in their pneumolysin genes. This resulted in the expression of nonhemolytic forms of pneumolysin. All of the strains producing nonhemolytic pneumolysin were sequence type 306 (ST306), whereas those producing "wild-type" pneumolysin were ST227. The mutations were in a region of pneumolysin involved in pore formation. These mutations can be made in vitro to give the nonhemolytic phenotype. Pneumolysin is generally conserved throughout all serotypes of S. pneumoniae and is essential for full invasive disease; however, it appears that serotype 1 ST306 does not require hemolytically active pneumolysin to cause IPD.

Neutrophil apoptosis, activation and anti-inflammatory cytokine response in granulocyte colony-stimulating factor-treated patients with community-acquired pneumonia

BACKGROUND

Despite antibiotic treatment, the mortality of severe community-acquired pneumonia (CAP), especially in patients with severe comorbidity, remains high. Innate defense mechanisms including polymorphonuclear neutrophil (PMN) activation and survival, orchestrated by cytokines, are primarily responsible for the elimination of bacterial organisms from the alveolus.

OBJECTIVES

The aim of this study was to evaluate the effect of granulocyte colony-stimulating factor (G-CSF) on PMN activation, apoptosis and cytokine response in patients with CAP.

METHODS

Patients received a single dose of G-CSF (1 x 300 or 480 microg s.c.) prior to standard antibiotic treatment (n=8) or standard treatment only (n=8). Apoptosis rate and expression of CD11b, CD66b, CD64 and CD114 surface molecules on systemic PMN were assessed using fluorescence-activated cell sorter analysis. Levels of the interleukin-1 receptor antagonist (IL-1 RA), the soluble tumor necrosis factor receptor inhibitor (sTNF-p55) and G-CSF were measured by ELISA.

RESULTS

In the treatment group, 12 h after G-CSF application, neutrophil count increased, neutrophil activation marker CD11b was stimulated (CD11b: 48.6+/-9.7 vs. 71.2+/-17.7, p<0.01), neutrophil apoptosis decreased (apoptosis: 1.36+/-0.27 vs. 0.2+/-0.12%, p <.01) and the concentration of IL-1RA and sTNF-p55 increased (IL-1RA 136.4+/-72.2 vs. 340.1+/-194.6 ng/ml, p<0.01; sTNF-p55,382+/-4,243 vs. 632+/-4,714 ng/ml, p<0.01; control group nonsignificant). These effects were not seen in the control group.

CONCLUSIONS

The application of a single dose of G-CSF in patients with CAP caused a prolonged survival and increased activation of neutrophils combined with a sustained release of anti-inflammatory cytokines.